bpo-32951: Disable SSLSocket/SSLObject constructor (#5864)

Direct instantiation of SSLSocket and SSLObject objects is now prohibited.
The constructors were never documented, tested, or designed as public
constructors. The SSLSocket constructor had limitations. For example it was
not possible to enabled hostname verification except was
ssl_version=PROTOCOL_TLS_CLIENT with cert_reqs=CERT_REQUIRED.

SSLContext.wrap_socket() and SSLContext.wrap_bio are the recommended API
to construct SSLSocket and SSLObject instances. ssl.wrap_socket() is
also deprecated.

The only test case for direct instantiation was added a couple of days
ago for IDNA testing.

Signed-off-by: Christian Heimes <christian@python.org>

1 files changed, 67 insertions, 71 deletions

diff --git a/Lib/ssl.py b/Lib/ssl.py
index 94ea35e..75ebcc1 100644
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -390,24 +390,24 @@ class SSLContext(_SSLContext):
                     server_hostname=None, session=None):
         # SSLSocket class handles server_hostname encoding before it calls
         # ctx._wrap_socket()
-        return self.sslsocket_class(
+        return self.sslsocket_class._create(
             sock=sock,
             server_side=server_side,
             do_handshake_on_connect=do_handshake_on_connect,
             suppress_ragged_eofs=suppress_ragged_eofs,
             server_hostname=server_hostname,
-            _context=self,
-            _session=session
+            context=self,
+            session=session
         )
 
     def wrap_bio(self, incoming, outgoing, server_side=False,
                  server_hostname=None, session=None):
         # Need to encode server_hostname here because _wrap_bio() can only
         # handle ASCII str.
-        return self.sslobject_class(
+        return self.sslobject_class._create(
             incoming, outgoing, server_side=server_side,
             server_hostname=self._encode_hostname(server_hostname),
-            session=session, _context=self,
+            session=session, context=self,
         )
 
     def set_npn_protocols(self, npn_protocols):
@@ -612,14 +612,23 @@ class SSLObject:
      * Any form of network IO incluging methods such as ``recv`` and ``send``.
      * The ``do_handshake_on_connect`` and ``suppress_ragged_eofs`` machinery.
     """
+    def __init__(self, *args, **kwargs):
+        raise TypeError(
+            f"{self.__class__.__name__} does not have a public "
+            f"constructor. Instances are returned by SSLContext.wrap_bio()."
+        )
 
-    def __init__(self, incoming, outgoing, server_side=False,
-                 server_hostname=None, session=None, _context=None):
-        self._sslobj = _context._wrap_bio(
+    @classmethod
+    def _create(cls, incoming, outgoing, server_side=False,
+                 server_hostname=None, session=None, context=None):
+        self = cls.__new__(cls)
+        sslobj = context._wrap_bio(
             incoming, outgoing, server_side=server_side,
             server_hostname=server_hostname,
             owner=self, session=session
         )
+        self._sslobj = sslobj
+        return self
 
     @property
     def context(self):
@@ -741,72 +750,48 @@ class SSLObject:
 class SSLSocket(socket):
     """This class implements a subtype of socket.socket that wraps
     the underlying OS socket in an SSL context when necessary, and
-    provides read and write methods over that channel."""
-
-    def __init__(self, sock=None, keyfile=None, certfile=None,
-                 server_side=False, cert_reqs=CERT_NONE,
-                 ssl_version=PROTOCOL_TLS, ca_certs=None,
-                 do_handshake_on_connect=True,
-                 family=AF_INET, type=SOCK_STREAM, proto=0, fileno=None,
-                 suppress_ragged_eofs=True, npn_protocols=None, ciphers=None,
-                 server_hostname=None,
-                 _context=None, _session=None):
-
-        if _context:
-            self._context = _context
-        else:
-            if server_side and not certfile:
-                raise ValueError("certfile must be specified for server-side "
-                                 "operations")
-            if keyfile and not certfile:
-                raise ValueError("certfile must be specified")
-            if certfile and not keyfile:
-                keyfile = certfile
-            self._context = SSLContext(ssl_version)
-            self._context.verify_mode = cert_reqs
-            if ca_certs:
-                self._context.load_verify_locations(ca_certs)
-            if certfile:
-                self._context.load_cert_chain(certfile, keyfile)
-            if npn_protocols:
-                self._context.set_npn_protocols(npn_protocols)
-            if ciphers:
-                self._context.set_ciphers(ciphers)
-            self.keyfile = keyfile
-            self.certfile = certfile
-            self.cert_reqs = cert_reqs
-            self.ssl_version = ssl_version
-            self.ca_certs = ca_certs
-            self.ciphers = ciphers
-        # Can't use sock.type as other flags (such as SOCK_NONBLOCK) get
-        # mixed in.
+    provides read and write methods over that channel. """
+
+    def __init__(self, *args, **kwargs):
+        raise TypeError(
+            f"{self.__class__.__name__} does not have a public "
+            f"constructor. Instances are returned by "
+            f"SSLContext.wrap_socket()."
+        )
+
+    @classmethod
+    def _create(cls, sock, server_side=False, do_handshake_on_connect=True,
+                suppress_ragged_eofs=True, server_hostname=None,
+                context=None, session=None):
         if sock.getsockopt(SOL_SOCKET, SO_TYPE) != SOCK_STREAM:
             raise NotImplementedError("only stream sockets are supported")
         if server_side:
             if server_hostname:
                 raise ValueError("server_hostname can only be specified "
                                  "in client mode")
-            if _session is not None:
+            if session is not None:
                 raise ValueError("session can only be specified in "
                                  "client mode")
-        if self._context.check_hostname and not server_hostname:
+        if context.check_hostname and not server_hostname:
             raise ValueError("check_hostname requires server_hostname")
-        self._session = _session
+
+        kwargs = dict(
+            family=sock.family, type=sock.type, proto=sock.proto,
+            fileno=sock.fileno()
+        )
+        self = cls.__new__(cls, **kwargs)
+        super(SSLSocket, self).__init__(**kwargs)
+        self.settimeout(sock.gettimeout())
+        sock.detach()
+
+        self._context = context
+        self._session = session
+        self._closed = False
+        self._sslobj = None
         self.server_side = server_side
-        self.server_hostname = self._context._encode_hostname(server_hostname)
+        self.server_hostname = context._encode_hostname(server_hostname)
         self.do_handshake_on_connect = do_handshake_on_connect
         self.suppress_ragged_eofs = suppress_ragged_eofs
-        if sock is not None:
-            super().__init__(family=sock.family,
-                             type=sock.type,
-                             proto=sock.proto,
-                             fileno=sock.fileno())
-            self.settimeout(sock.gettimeout())
-            sock.detach()
-        elif fileno is not None:
-            super().__init__(fileno=fileno)
-        else:
-            super().__init__(family=family, type=type, proto=proto)
 
         # See if we are connected
         try:
@@ -818,8 +803,6 @@ class SSLSocket(socket):
         else:
             connected = True
 
-        self._closed = False
-        self._sslobj = None
         self._connected = connected
         if connected:
             # create the SSL object
@@ -834,10 +817,10 @@ class SSLSocket(socket):
                         # non-blocking
                         raise ValueError("do_handshake_on_connect should not be specified for non-blocking sockets")
                     self.do_handshake()
-
             except (OSError, ValueError):
                 self.close()
                 raise
+        return self
 
     @property
     def context(self):
@@ -1184,12 +1167,25 @@ def wrap_socket(sock, keyfile=None, certfile=None,
                 do_handshake_on_connect=True,
                 suppress_ragged_eofs=True,
                 ciphers=None):
-    return SSLSocket(sock=sock, keyfile=keyfile, certfile=certfile,
-                     server_side=server_side, cert_reqs=cert_reqs,
-                     ssl_version=ssl_version, ca_certs=ca_certs,
-                     do_handshake_on_connect=do_handshake_on_connect,
-                     suppress_ragged_eofs=suppress_ragged_eofs,
-                     ciphers=ciphers)
+
+    if server_side and not certfile:
+        raise ValueError("certfile must be specified for server-side "
+                         "operations")
+    if keyfile and not certfile:
+        raise ValueError("certfile must be specified")
+    context = SSLContext(ssl_version)
+    context.verify_mode = cert_reqs
+    if ca_certs:
+        context.load_verify_locations(ca_certs)
+    if certfile:
+        context.load_cert_chain(certfile, keyfile)
+    if ciphers:
+        context.set_ciphers(ciphers)
+    return context.wrap_socket(
+        sock=sock, server_side=server_side,
+        do_handshake_on_connect=do_handshake_on_connect,
+        suppress_ragged_eofs=suppress_ragged_eofs
+    )
 
 # some utility functions